Electric rivet heater



June 16, 1925. 1,542,008

J. E. SEDERHOLM ELECTRIC RIVET HEATER Filed Aug. 5, 1922 4 Sheets-Sheet l 36' 28 37 N VEN TOR JOHN L. 6550551401.!

Patented June 16, 1925.

UNITED STATES PATENT orrlcs.

JOHN E. SEDERHOLM, OF ST. PAUL, MINNESOTA, ASSIGNOB TO AMERICAN HOI ST & DERRICK COMPANY, OF ST. PAUL, MINNESOTA, A CORPORATION OF MINNESOTA.

ELECTRIC RIVET HEATER.

Application filed August 5, 1922. Serial 110,57 ,940. 7

To all whom it may concern:

Be it known that I, JOHN E. SEDERHOLM, a citizen of the United States, resident of St. Paul, in the county of Ramsey and State of Minnesota, have invented certain new and useful Improvements in Electric Rivet Heaters, of which the following is a specification.

This invention. relates to improvements in electric heaters designed, particularly for heating rivets for use in hot-riveting structural steel frames for buildings, bridges, etc.

The primary object of my invention is to provide a rivet heater capable of being operated to full capacity, continuously and with a high degree of efliciency.

A further object of the invention is to provide a rivet heater having each of its secondary coils or'elements constructed of one piece,and, of practically an E form, so as to be in close proximity with the magnetic core, thus, allowing practically all of the magnetic lines of force, set up in the core by the primary coils, to act upon said coils or elements when the circuit is closed.

A further object is to provide a rivet heater having removably mounted jaws, or contact blocks, for holding the rivets, so that should the contacts become damaged from wear .or arcing they may readily and quickly be removed for replacement without disturbing the secondary elements. c

A further object is to provide a rivet heater capable of heating rivets of various lengths without the necessity of adjustmerits, and also one in which a number of rivets may be heated simultaneously.

Other objects of the invention will 'inore fully appear from the following description and the accompanying drawings, and will be pointed out in the annexed claims:

The drawings vdisclose a structure designed to'carry out the objects of the in vention, but it is to be understood that the invention is not confined to the exact details or features shown, as various changes may be made within the scope of the claims which follow.

In the drawings:

Figure 1 is a fronteleva-tion of an electric rivet heater embodying my invention.

Figure 2 is a transverse sectional view sh wing an at the se s w el m place on the magnetic core and the means for operating the rivet holding jaws.

Figure 3 is a top View showing the general arrangement of the different parts.

Figure 4 is a longitudinal sectional'view on the line 44. of; Figure 2 and showing the arrangement of the primary coils and the secondary elements on the magnetic core. V

Figure 5 is a fragmentary view of the insulated joint on one of the push rods for operating the upper jaws.

Figure 6 is a wiring diagram of the apparatus.

, In the embodimentof the invention here shown, there is disclosed a frame consisting of a. pair of front legs 7 and rear legs 8, preferably of angl iron. The front and rear leg on each. side are preferably secured together near the bottom by a cross member 9 riveted thereto, and near the center section by a tie-rod 10. A magnetic core 11, constructed of laminated sheet steel, preferably rectangular in shape, is securely clamped between the front and rear legs, at the top, by bolts 12-, thus providing a very rugged and substantial frame.

The upper and lower parallel longitudinally extending members of the; magnetic core 11 are covered with a suitable insulat-1 ing material 13. On the upper member of this core are mounted two primary coils 14:, one adjacent each end. while on the lower member, and directly beneath thecoils 14,- two similar coils 15 are mounted.

Two secondary elements 16, preferably of copper and of substantially theletter E in form, (Fig. 2) are disposed upon the core 11, adjacent the primary coils, and are insulated therefrom by sheets'of suitable insulating material 17,, such as asbestos or in terposed between said members, asshown in Figure 4. A bar 18, preferably of angle iron, has its ends secured to the rear of the frame by bolts 19, with its central portion bearing against the rear faces of the secondary elements, thus, securely clamping said elements in their respective places upon the magnetic core. This bar is. also insulated from said elements by suitable insulation 21. The object of forming the secondary elements as above described is to provide an element which will snugly fit the longitii dinal member of the core, when mount CJI wherein contact. hiotl are slidahly mounted. These hloi a re reta inert in their res iective seats o stud holts sccured to the torward l ar-es o the elements and projecting forwardly through elongated apertures provided in said hlo lcs. Guide or hearing plates 25. aperture-l to receive the ends of the holts are pla cc. on said bolts and resiliently held a;- ainst the contact hloclts 2 3 h compression springs 26 and nuts 2?. B the ahove means the con tact l'ilocks are held in close contact with the secondary elements at al times. An inwardl extending lug; provided on each of the blocks 23 tor use when heating long rivets, (Figure l) Two stationary contact hlock. 29 are rigidly secured to the central portions of the secondary elements hy holts 3t. and are arranged to he in a direct line with the upper and lower contact lllUCh'Fl their inner portions projecting inwardly and (IO-Olifilfillllll f with the lugs 28 in holding long holts as shown in Figure l.

The above construction provides a very simple and practica. means for gripping and holding the rivets while the are hein; heated. and also should any 01'" the contact blocks hecome damaged due to wear and arcing they may readily he remored tor replacement without disturhingz' the secondarv elements.

The two upper contact hlocks are operated by means of toot pedals 32. pivotall v mounted on a shalt 3 h secured to the cross mcmher 9 of: the trame. These pedals have rearwardly extending arms ll. pretcrahlfv integral therewith. to which connectingrods 35 are pivotallv connected at 36. the upper ends of said rods heing pivotally connected with the contact l)lO0l S as shown at Coiled tension springs 39 are provided to yieldingly hold the contact hloclcs and the pedals in their normal position against a stop secured to the frame. To prevent the foot pedals 32 from hecon'rilur energized when a rivet is inserted hetw eca the contact blocks for heating, it is nece. arv to insulate said blocks from the pedal corinecting rods. This I have shown, as hcine; effected by providing a non-conductive. or insulated joint at]. in the connecting rods 5.

The two lower contact hloclts a re operated in a similar manner hy lootpedals 42:3. also mounted on the shatt, il Conruwtimr rods et l connect the pedals to the Hooks and the springs retain the hlocl-zs and pedals in their normal position against the stop 3 A switch panel *l-l is provided and pretcrahlfv secured to one oi the torwanl lt'jl'fj T within convenient reach of the operator. [loon this panel there mounted a heat regulating: switch l1 ior i'tflthtl the temperature to which the rivets are heated, and also a ontrol switch i tor opening and closing: th cir uit. to the main line. (Figures 1 and t3.)

The reJrulatim switch iii is prt s'itlttl with three contact posts l4". l3. and til. (Z more (Ll The low heat post l? is electrically conn ctcd h a comluctor 51 to an clcctroinae'iact and a. conductor 53 conne'ls th Phct'i'w magnet to the main line wire 5!. The, medium heat post th connccte-Il to the wi e hy the condiu-tor 57 clc tr nnarrnet Fit; and conductor Iii. and the high h at post 49 is similartr connected lrv the con: -tor 55%. cltartrounurnct 3 and conductor it. The regulating switch to is connect d ry a conductor tr, to a contact post tti-i on the ontrol switch 46.

i conductor at connects this switch to the main l ne ire 65. Thus when the rcgnlat inc; switch to has heen adjusted to the desired heat as shown on the wirino' dia- {.rrain. (Figure ti) and the switch ll, srloscil. a complete circuit will he tormcd: the currentpassing troni the wire 65 through the conductor (it to the sw tch l-ti. tron] the switch +1. 6 through the coiuluctor (32 to the switch 45s thence throusrh the conductor electromagnet 56 and conductor 57 to the main line wire at. The ahovo descrihed circuits will hereinafter he ret'erred to as th secondary circuits. as a matter of distinc tion hetwccu said circui s and the primary or heatinc circuits.

The primary circuits are provided with nurlnctieallv operated switches 67K 39. and (39. which atrtomaticallv open and close through energization oi the electromagncts 52, 56. and 5th in the sccondar circuits. Thus. when the regulating switch t?) in the position shown in the wiring diagram and the control switch it; closed. closin; of the switch (38 will antomaticall he cittected by the electromagnet 5t). The current will he conducted from the main line wire 65 through a conductor Tl. to the primary coils lit. through these oils to terminal posts Til, thence. through conductors T t. terminal posts 7;? connected with the pri mary coils 15. These latter coils are also provided with terminal posts 74:. 75, and it; corresponding; to the three contact posts 457, 4:8 and t9 on the regulating switch L). Thus when the switch 413 in contact with the llti cuits are similarly connected. connectors and 83 electrically connect the coils 15' to the switch" 69,'when high heatisdes'ired, and conductors 84 and 85* connect the coils for theswitch't'i' whehl'ow heat is 'ui're'd;

F romthe foregoing, theretorel rt will be noted that when the regiilatin'gswitch is in contactwith the low heat post 47,-all ot the ampere turns of the primary coils 15-willbe in circuit which will reduce fiheam er'age flow in the coils and cause saidcoils" to be come heated to a" comparatively low temperature. Conversely wheh the switch 45 is moved inmcontact with the lllg'lilleitt post 49, a numbe -"of the numer c turns of the coils 15 will-be cutout! of" the cireuinthere;

by increasing the amperage'tlbw in sai'dcoils with the result that they will" become: heated to a relatively higher temperature or high-heat; v

The operation of this apparatus may be explainedas follows with reference to Figures land 6": y,

First, the regulating switch -15 is adjust'ed to the desired heat- I have Here shown it in Contact with the niedinnr hear t 48. The control switch 46 is then close allowing the current to flow through the mediimiheat primary circuit.- As the current passes through the coils 14 and 15, the magnetic core 11, on which they are mounted becomes energized, said core in turn energizing the two secondary elements mounted thereon. The voltage in the secondary elements is very low, being normally one volt, or less, but the current density very high, due to the current carrying capacity of said elements. Assuming now that a rivet is inserted between the upper right contact block 23 and the stationary block 29, (Figure 1), the current will flow from the block 23 throughthe rivetto the block 29, thence, around the magnetic core 11 back to the block 23, thus forming a complete circuit around the core. (Figure 6.) Owing to the inferior carrying capacity of the rivet due to its very low current density, it immediately starts to heat. As soon as it has attained the desired degree of heat it is removed and the next rivet inserted. Rivets inserted between the lower contact blocks 23 and the stationary blocks 29 are heated in a similar manner, the current passing from the block 29 through the rivet to the block 23, thence, around the lower section of the core 11 and back to the desired to heat rivets which are" foundto be too long to, be inserted between" the blocks 29 and 23', they may inse'rtedbetween the stationary block 29 and the lu'g28 provided on the movable blocks 23' as indicated in Figure 1. The operation of the low and high heats is similar to that of the medium' heat above described, differing only by increasing or decreasing the number of anipei'e turns in the primary coi'lfslfiby tapping said coils'as' hereinbcfore described. \Vith this improved type of rivet heater, rivets of various diameters and lengthsmay be heated at one time thus greatly increasingthe capacity and efficiency of the apparatus.

As here shown, the magnetic core 11 is in the form of a rectangular frame. with the primary coils 14 arranged upon the upper longitudinal member of the frame, and the primary coils 15 upon the" lower longitudinal 1116111561 of said" frame. The E-shaped secondary elements 16, 16, are each provided with three branches extending at right anglesto the main or back member thereof." The center horizontal branch extends between the upper and lower longitudinal members of the core 11", while the upper and lower branches there 01 extend one above the upper longitudinal member, and the other below the lower longitudinal member of said core 11. Said branches fit snugly against the walls of the" core as shown in Figure Each of said secondary elements maybe considered as constituting a double u shaped member, and the entire element is, therefore, of substantially E-shape. When a rivet is inserted, it completes a circuit either through the upper and middle branches of the secondary element, or through the lower and middle branches of said element, depending upa rectangular frame, of primary coils ary ranged on the longitudinal parallel members of said core, secondary elements of substantially E-shape, with their branches extending above and below the longitudinal members of said core, and means on the ends of said branches for holding rivets between the middle branch of said secondary element, and the upper or lower branch thereof.

2. In a device of the class described, the combination with a magnetic core, having longitudinally extending parallel members, of primary coils arranged on the parallel members of said core, secondary elements of substantially E-shape with their branches extending transversely above and below, and fitting against, the longitudinal members of said core, means for securing said secondary elements in position, and means on the ends of said branches for holding articles to be heated between adjacent ends of said branches.

3. In a device ot the class described, the con'ibination with a magnetic core constructed of laminated sheet steel, and rectangular in form, o't primary coils mounted on the upper and lower members 0t said core, a secondary element havingbranches projecting between. above and below the core members, a stationary block arranged upon the central branch of the secondary element, slidable contact blocks arranged upon the upper and lower branches of said element, and constructed to hold rivets, or similar articles, to be heated, between the stationary block and either of the slidable blocks, and means for moving said slidable blocks towards or from said stationary block.

4:. In a device of the class described, the combination with a magnetic core constructed of laminated sheet steel. and rectangular in form, of primary coils mounted on the upper and lower members of said core, a pair of secondary elements. each element having branches projecting between, :bove and below the core men'ibers, a stationary block arranged upon the central branch of each secondary element, slidable contact blocks arranged upon the upper and lower branches of each element. and constructed to hold rivets or similar articles to be heated between the stationary block and either of the slidable blocks, and means for moving said slidable blocks toward or from said stationary block.

5. In an electric rivet heater, the combination with a n'iagnetic core, of primary coils, a secondary element having a central branch extending between an upper and a lower member of said core, and an upper and lower branch respectively above the upper member and below the lower member of said core, and means for holding rivets between the middle branch of said secondary element and th upper or the lower branch thereof.

6. In an electric rivet heater, the combi nation with a magnetic core, of primary coils arranged on longitudinal members of said core, secondary elements having upper. lower and middle branches extending above and below the longitudinal members of said core, and means on said branches for bolding rivets between the middle branch of said secondary element and the upper or lower branch thereof.

7. Tn an electric rivet. heater, the combi nation with a magnetic core, of primary coils arranged on said core. secondary elements of substantially E shape with their branches extending above and below the members of said core, and means on said branches for holding rivets between the middle branch of said secondary element and the upper or lower branch thereof.

In witness whereof, I have hereunto set my hand this 2nd day of August, 1922.

JOHN E. SEDERHOLM.

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